convert where to if else style code in fortran.

hi below is the code I rewrote(with do loops) and further down(with where statements) is the original code. The code seems to be producing differnt values for WORK arrays over time. How to resolve this issue?? 

do j=1,ny_block
           do i=1,nx_block

           if(LMASK(i,j) .eq. .true. )then

            WORK1(i,j,kk) =  KAPPA_THIC(i,j,kbt,k,bid)  &
                           * SLX(i,j,kk,kbt,k,bid) * dz(k)

            WORK2(i,j,kk) = c2 * dzwr(k) * ( WORK1(i,j,kk)            &
              - KAPPA_THIC(i,j,ktp,k+1,bid) * SLX(i,j,kk,ktp,k+1,bid) &
                                            * dz(k+1) )

            WORK2_NEXT(i,j) = c2 * ( &
              KAPPA_THIC(i,j,ktp,k+1,bid) * SLX(i,j,kk,ktp,k+1,bid) - &
              KAPPA_THIC(i,j,kbt,k+1,bid) * SLX(i,j,kk,kbt,k+1,bid) )

            WORK3(i,j,kk) =  KAPPA_THIC(i,j,kbt,k,bid)  &
                           * SLY(i,j,kk,kbt,k,bid) * dz(k)

            WORK4(i,j,kk) = c2 * dzwr(k) * ( WORK3(i,j,kk)            &
              - KAPPA_THIC(i,j,ktp,k+1,bid) * SLY(i,j,kk,ktp,k+1,bid) &
                                            * dz(k+1) )

            WORK4_NEXT(i,j) = c2 * ( &
              KAPPA_THIC(i,j,ktp,k+1,bid) * SLY(i,j,kk,ktp,k+1,bid) - &
              KAPPA_THIC(i,j,kbt,k+1,bid) * SLY(i,j,kk,kbt,k+1,bid) )

            endif

           enddo
          enddo

           where ( LMASK )

            WORK1(:,:,kk) =  KAPPA_THIC(:,:,kbt,k,bid)  &
                           * SLX(:,:,kk,kbt,k,bid) * dz(k)
            WORK2(:,:,kk) = c2 * dzwr(k) * ( WORK1(:,:,kk)            &
              - KAPPA_THIC(:,:,ktp,k+1,bid) * SLX(:,:,kk,ktp,k+1,bid) &
                                            * dz(k+1) )

            WORK2_NEXT = c2 * ( &
              KAPPA_THIC(:,:,ktp,k+1,bid) * SLX(:,:,kk,ktp,k+1,bid) - &
              KAPPA_THIC(:,:,kbt,k+1,bid) * SLX(:,:,kk,kbt,k+1,bid) )

            WORK3(:,:,kk) =  KAPPA_THIC(:,:,kbt,k,bid)  &
                           * SLY(:,:,kk,kbt,k,bid) * dz(k)
            WORK4(:,:,kk) = c2 * dzwr(k) * ( WORK3(:,:,kk)            &
              - KAPPA_THIC(:,:,ktp,k+1,bid) * SLY(:,:,kk,ktp,k+1,bid) &
                                            * dz(k+1) )

            WORK4_NEXT = c2 * ( &
              KAPPA_THIC(:,:,ktp,k+1,bid) * SLY(:,:,kk,ktp,k+1,bid) - &
              KAPPA_THIC(:,:,kbt,k+1,bid) * SLY(:,:,kk,kbt,k+1,bid) )

          endwhere

Are they equivalent??

Coz I am having issues of correctness here.